A vehicle such as a car is provided with a wiper device that wipes off rain drops adhered to a windshield or splash from a preceding car so as to secure a driver's visibility in rainy weather. The wiper device has a wiper arm whose swinging is controlled by a wiper driving device. A wiper blade that abuts against the windshield is attached to a leading end of the wiper arm. The wiper arm is swung by converting rotary motion of a motor into reciprocating motion by a link mechanism. The reciprocating motion of the wiper arm causes the wiper blade to perform wiping operation on the windshield.
It is known that the wiper device provided in a car or the like has a system that detects a current position of the wiper arm on a glass surface and makes the wiper blade perform reciprocal wiping operation between upper/lower inversion positions based on the detected data (see, for example, Japanese Application Publication 2010-173338). In such a wiper device, in controlling the operation of the wiper arm, an arm target speed is set corresponding to an angular position of the wiper arm. A wiper control device detects the current position of the wiper arm and then feedback-controls a wiper motor based on the arm current position and target speed to make the wiper blade perform reciprocal wiping operation between upper/lower inversion positions.
Further, as to the operation control of the wiper device, Japanese Application Publication 2013-14295 discloses a system that sets an acceleration region and a deceleration region in one-way (forward path or backward path) wiping operation so as to achieve smooth wiping operation without a sense of incongruity.
In the acceleration region, a difference between a maximum rotation speed of the motor and target speed of the motor at the current angle is calculated every time the angular position of the arm advances. Then, a next target speed is set by adding 1/x of the calculated difference to the current target speed. In the deceleration region, a next target speed is set by subtracting 1/(x−1) of the above calculated difference from the current target speed. In setting the next target speeds, for achieving smooth wiping operation without a sense of incongruity, the addition amount and subtraction amount of the speed are set such that a target speed curve at acceleration time and that at deceleration time are approximately symmetric.
However, in actual wiping operation, a load amount of the motor is not always equal over the entire wiping range depending on a condition of a surface of the windshield or due to influence of traveling wind. Thus, when the target speed curves at the acceleration and deceleration times are symmetric, unevenness may occur in a blade moving speed in continuous reciprocating operation, which may prevent achievement of the smooth wiping operation without a sense of incongruity.